Vehicular image sensing system

ABSTRACT

An image sensing system for a vehicle includes an imager disposed at or proximate to an in-cabin portion of a vehicle windshield and having a forward field of view to the exterior of the vehicle through the vehicle windshield. The photosensor array of the imager is operable to capture image data. The image sensing system identifies objects in the forward field of view of the imager via processing of captured image data by an image processor. The photosensor array may be operable to capture frames of image data and the image sensing system may include an exposure control which determines an accumulation period of time that the photosensor array senses light when capturing a frame of image data. Identification of objects may be based at least in part on at least one of (i) shape, (ii) luminance, (iii) geometry, (iv) spatial location, (v) motion and (vi) spectral characteristic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/550,064, filed Jul. 16, 2012, now U.S. Pat. No. 8,324,552, which is acontinuation of U.S. patent application Ser. No. 13/204,106, filed Aug.5, 2011, now U.S. Pat. No. 8,222,588, which is a continuation of U.S.patent application Ser. No. 12/640,425, filed Dec. 17, 2009, now U.S.Pat. No. 7,994,462, which is a continuation of U.S. patent applicationSer. No. 12/273,879, filed Nov. 19, 2008, now U.S. Pat. No. 7,655,894,which is a continuation of U.S. patent application Ser. No. 11/626,535,filed Jan. 24, 2007, now U.S. Pat. No. 7,459,664, which is acontinuation of U.S. patent application Ser. No. 11/545,039, filed Oct.6, 2006, now U.S. Pat. No. 7,402,786, which is a continuation of U.S.patent application Ser. No. 09/441,341, filed Nov. 16, 1999, now U.S.Pat. No. 7,339,149, which is a continuation of U.S. patent applicationSer. No. 09/135,565, filed Aug. 17, 1998, now U.S. Pat. No. 6,097,023,which is a continuation of U.S. patent application Ser. No. 08/621,863,filed Mar. 25, 1996, now U.S. Pat. No. 5,796,094.

BACKGROUND OF THE INVENTION

This invention relates generally to vehicle control systems and, inparticular, to a system and method for controlling the headlights of thevehicles. The invention is particularly adapted to controlling thevehicle's headlamps in response to sensing the headlights of oncomingvehicles and taillights of leading vehicles.

It has long been a goal to automatically control the state of avehicle's headlights in order to accomplish automatically that which ismanually performed by the driver. In particular, the driver of a vehiclewhose headlights are in a high-beam state will dim the headlights uponconscious realization that the headlights are a distraction to thedriver of an oncoming vehicle or a leading vehicle. It is desirable torelieve the driver of such duties and thereby allow the driver toconcentrate on the driving task at hand. The ideal automatic controlwould also facilitate the use of high beams in conditions which allowtheir use, increasing the safety for the controlled vehicle as well asreducing the hazard caused by the occasional failure of the driver todim the headlights when such headlights are distracting another driver.

Prior attempts at vehicle headlight dimming controls have included asingle light sensor which integrates light in the scene forward of thevehicle. When the integrated light exceeds a threshold, the vehicleheadlights are dimmed. Such approaches have been ineffective. Theheadlights of oncoming vehicles are, at least from a distance, pointsources of light. In order to detect such light sources in an integratedscene, it is necessary to set a sufficiently low threshold of detectionthat many non-point-sources at lower intensities are interpreted asheadlights or taillights. Such prior art vehicle headlight dimmingcontrols have also been ineffective at reliably detecting the taillightsof leading vehicles. The apparent reason is that the characteristics ofthese two light sources; for example, intensity, are so different thatdetecting both has been impractical. In order to overcome suchdeficiencies, additional solutions have been attempted, such as the useof infrared filtering, baffling of the optic sensor, and the like. Whilesuch modifications may have improved performance somewhat, the long-feltneed for a commercially useful vehicle headlight dimming control hasgone unmet.

SUMMARY OF THE INVENTION

The present invention provides a vehicle control which is capable ofidentifying unique characteristics of light sources based upon a preciseevaluation of light source characteristics made in each portion of thescene forward of the vehicle, in the vicinity of each light source, byseparating each light source from the remainder of the scene andanalyzing that source to determine its characteristics. Onecharacteristic used in identifying a light source is the spectralcharacteristics of that source which is compared with spectralsignatures of known light sources, such as those of headlights andtaillights. Another characteristic used in identifying a light source isthe spatial layout of the light source. By providing the ability toidentify the headlights of oncoming vehicles and the taillights ofleading vehicles, the state of the headlights of the controlled vehiclemay be adjusted in response to the presence or absence of either ofthese light sources or the intensity of these light sources.

This is accomplished according to an aspect of the invention byproviding an imaging sensor which divides the scene forward of thevehicle into a plurality of spatially separated sensing regions. Acontrol circuit is provided that is responsive to the photosensors inorder to determine if individual regions include light levels having aparticular intensity. The control circuit thereby identifies particularlight sources and provides a control output to the vehicle that is afunction of the light source identified. The control output may controlthe dimmed state of the vehicle's headlamps.

In order to more robustly respond to the different characteristics ofheadlights and taillights, a different exposure period is provided forthe array in order to detect each light source. In particular, theexposure period may be longer for detecting leading taillights andsignificantly shorter for detecting oncoming headlights.

According to another aspect of the invention, a solid-state lightimaging array is provided that is made up of a plurality of sensorsarranged in a matrix on at least one semiconductor substrate. Thelight-imaging array includes at least one spectral separation device,wherein each of the sensors responds to light in a particular spectralregion. The control circuit responds to the plurality of sensors inorder to determine if spatially adjacent regions of the field of viewforward of the vehicle include light of a particular spectral signatureabove a particular intensity level. In this manner, the controlidentifies light sources that are either oncoming headlights or leadingtaillights by identifying such light sources according to their spectralmakeup.

According to another aspect of the invention, a solid-statelight-imaging array is provided that is made up of a plurality ofsensors that divide the scene forward of the vehicle into spatiallyseparated regions, and light sources are identified, at least in part,according to their spatial distribution across the regions. This aspectof the invention is based upon a recognition that headlights of oncomingvehicles and taillights of leading vehicles are of interest to thecontrol, irrespective of separation distance from the controlledvehicle, if the source is on the central axis of travel of the vehicle.Oncoming headlights and leading taillights may also be of interest awayfrom this axis, or off axis, but only if the source has a higherintensity level and is spatially larger. These characteristics ofheadlights and taillights of interest may be taken into consideration byincreasing the resolution of the imaging array along this central axisor by increasing the detection threshold off axis, or both. Such spatialevaluation may be implemented by selecting characteristics of an opticaldevice provided with the imaging sensor, such as providing increasedmagnification central of the forward scene, or providing a widehorizontal view and narrow vertical view, or the like, or by arrangementof the sensing circuitry, or a combination of these.

The present invention provides a vehicle headlight control which isexceptionally discriminating in identifying oncoming headlights andleading taillights in a commercially viable system which ignores othersources of light including streetlights and reflections of thecontrolled vehicle's headlights off signs, road markers, and the like.The present invention further provides a sensor having the ability topreselect data from the scene forward of the vehicle in order to reducethe input data set to optimize subsequent data processing. The inventionis especially adapted for use with, but not limited to, photoarrayimaging sensors, such as CMOS and CCD arrays.

These and other objects, advantages, and features of this invention willbecome apparent upon review of the following specification inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a portion of a vehicle embodying theinvention;

FIG. 2 is a partial side elevation view and block diagram of a vehicleheadlight dimming control system according to the invention;

FIG. 3 is a block diagram of the control system in FIG. 2;

FIG. 4 is a layout of a light-sensing array useful with the invention;

FIG. 5 is a block diagram of an imaging sensor;

FIG. 6 is an alternative embodiment of an imaging sensor;

FIGS. 7 a-7 d are a flowchart of a control program;

FIGS. 8 a-8 c are spectral charts illustrating spectra regions usefulwith the invention;

FIG. 9 is the same view as FIG. 3 of another alternative embodiment;

FIG. 10 is the same view as FIG. 2 of an alternative mountingarrangement;

FIGS. 11 a-11 c are views forward of a vehicle illustrating differentforms of spatial filtering; and

FIGS. 12 a and 12 b are illustrations of use of the invention to detectparticular atmospheric conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now specifically to the drawings and the illustrativeembodiments depicted therein, a vehicle 10 includes a vehicle headlightdimming control 12 made up of an imaging sensor module 14 which senseslight from a scene forward of vehicle 10, an imaging control circuit 13which receives data from sensor 14, and a vehicle lighting control logicmodule 16 which exchanges data with control circuit 13 and controlsheadlamps 18 for the purpose of modifying the headlight beam (FIGS. 1and 2). Such control may be a binary control of the aim of the beam,such as by switching between lamps or lamp filaments, or may be acontinuous variation of the aim of a single lamp more or less forward ofthe vehicle. The control may also control the intensity or pattern ofthe beam. Additionally, the lights of a vehicle equipped with daytimerunning lights may be switched between a daytime running light conditionand a low-beam condition. Vehicle headlight dimming control 12 canperform a wide range of additional control operations on the vehicle,including turning the headlights ON and OFF, modifying the lightintensity of the instrument panel, and providing an input to anelectro-optic mirror system.

Vehicle lighting control logic module 16 receives an input 20 fromimaging control circuit 13. In particular embodiments, such as oneswhich adjust the state of the headlights between continuously variablestates, module 16 may supply data to imaging control circuit 13, such asthe speed of the vehicle, which may be combined with the data sensed byimaging sensor 14 in establishing the state of headlights 18. In theillustrated embodiment, imaging sensor module 14 may be fixedly mountedin a housing 28 by a bracket 34 mounted to, or near, the vehicle'swindshield 32. Bracket 34 also mounts an interior rearview mirror 30.This is a preferred mounting for imaging sensor module 14 because thelocation within the interior of the vehicle substantially eliminatesenvironmental dirt and moisture from fouling the light sensor module.Additionally, the position behind windshield 32, which typically is keptrelatively clear through the use of washers and wipers and the like,ensures a relatively clear view of the scene forward of vehicle 10.Alternatively, imaging sensor module 14 may be mounted within a housing29 of interior rearview minor 30 facing forward with respect to vehicle10 (FIG. 10). In such embodiment, control circuit 13 may be combinedwith the circuit which controls the partial reflectance level of minor30 if minor 30 is an electro-optic mirror such as an electrochromicmirror. Other mounting techniques for sensor module 14 will be apparentto the skilled artisan.

Imaging sensor module 14 includes an optical device 36, such as a lens,an array 38 of photon-accumulating light sensors, and a spectralseparation device for separating light from the scene forward of vehicle10 into a plurality of spectral bands, such as a filter array 40disposed between optical device 36 and light-sensing array 38.Light-sensing array 38 is described in detail in application Ser. No.08/023,918 filed Feb. 26, 1993, now U.S. Pat. No. 5,550,677, thedisclosure of which is hereby incorporated herein by reference.Light-sensing array 36 includes a plurality of photosensor elements 42arranged in a matrix of columns and rows (FIG. 4). In the illustratedembodiment, an array of 512 rows and 512 columns of light-sensingpixels, each made up of a photosensor element 42 is utilized. However, agreater or lesser number of photosensor elements may be utilized and maybe arranged in matrix that is laid out in other than columns and rows.Each photosensor element 42 is connected to a common word-line 44. Toaccess the photosensor array, a vertical shift register 46 generatesword-line signals to each word-line 44 to enable each row of photosensorelements 42. Each column of photosensor elements is also connected to abit-line 48 which is connected to an amplifier 50. As each word-line 44is accessed, a horizontal shift register 52 uses a line 54 to output thebit-line signals on consecutive bit lines 48 to an output line 56. Inthis manner, each photosensor element 42 may be individually accessed byappropriate manipulation of shift registers 46 and 52. Output 56 issupplied to a digital signal processor 13 which is supplied on an output62 as input to control circuit 13 (FIGS. 3-5).

Digital signal processor 13 includes an analog-to-digital converter 58which receives the output 56 of array 36 and converts the analog pixelvalues to digital values. A digital output 68 of A/D converter 58 issupplied to a taillight detection circuit 76, a headlight detectioncircuit 78, and to ambient sense logic circuit 84. A detection controlcircuit 72 supplies control and timing signals on a line 74 which issupplied to array 38, A/D converter 58 taillight detection circuit 76,headlight detection circuit 78, and ambient sense logic 84. Such signalscoordinate the activities of these modules and provide any data, fromlook-up tables provided in control circuit 72, needed by each circuit toperform its function. For example, control circuit 72 may provideintensity threshold levels to taillight detection circuit 76 andheadlight detection circuit 78.

Taillight detection circuit 76 detects a red light source having anintensity above a particular threshold as follows. For each pixel thatis “red,” a comparison is made with adjacent “green” pixels and “blue”pixels. If the intensity of a red pixel is more than a particular numberof times the intensity of the adjacent green pixel and adjacent bluepixel, then it is determined that the light source is red. If theintensity of the “red” light source is greater than a particularthreshold, an indication is provided at 80.

Headlight detection circuit 78 detects a white light source having anintensity above a particular threshold as follows. A white light is acombination of red, green, and blue components. If adjacent “red,”“green,” and “blue” pixels all exceed a particular threshold, a ratiocomparison is made of the pixels. If the ratio of the intensity of theadjacent “red,” “green,” and “blue” pixels is within a particular range,such as 20 percent by way of example, then a white light source isdetected.

Vehicle headlight dimming control 12 additionally includes an ambientlight-sensing circuit 84 which receives an input from digital outputsignal 68. Ambient detection circuit 84 samples a subset of photosensorelements and detects light levels sensed by the subset over a longperiod of time in order to produce significant time filtration.Preferably, the photosensor elements in the sensed subset includesensors that detect portions of the forward-looking scene that are justabove the earth's horizon which is more indicative of the ambient lightcondition. Ambient detection circuit 84 produces an indication 88 ofambient light levels which is supplied as an input to a lighting controlmodule 90. A high ambient light level may be used by a module 90 toinhibit headlight actuation or to switch headlights 18 to a daytimerunning light mode. Ambient detection circuit 84 can, optionally,perform other functions, such as switching the daytime running lights ofthe vehicle between daytime and nighttime modes, controlling theintensity of the vehicle's instrument panel and providing an input to anelectro-optic rearview minor system.

Indications 80 and 82 from the light detection units and indication 88from ambient detection circuit 84 are supplied to a lighting controlcircuit 90 which produces a first indication 92 that headlights 18 areto be switched on, or switched from a daytime running condition to anight mode, and a high-beam enable indication 94 that the headlights maybe switched to a high-beam state. Vehicle lighting control logic module16 responds to indications 92 and 94 by switching headlights 18 to anappropriate mode. An output 96 from module 16 may be provided to supplylighting control circuit 90 with information with respect to vehicletelemetry, steering, speed, and any other parameter that may beincorporated into the algorithm to determine the state of the headlightsof the vehicle. Digital signal processor 13 may be implemented usingdiscrete digital circuit modules or with a suitably programmedmicro-processor with input and output buffers.

In one embodiment, an imaging sensor module 14 a includes a singlephotosensor array 38 a, one spectral filter array 40 a, and one opticaldevice 36 a (FIG. 5). In this illustrated embodiment, spectral filterarray 40 a includes alternating spectrum filter elements for exposingadjacent pixels to different regions of the electromagnetic spectrum inthe red band or green band or blue band. This may be accomplished byarranging such filter elements in stripes or by alternating filterspectral regions in a manner known in the art. Digital signal processor13 a captures a frame of data by enabling photosensor array 38 a for aparticular exposure period during which each photosensor element 42accumulates photons. In order to detect oncoming headlights, digitalsignal processor 13 a enables photosensor array 38 a for a firstexposure period. In order to detect leading taillights, digital signalprocessor 13 a enables photosensor array 38 a for a second exposureperiod. Because oncoming headlights have an intensity level that issubstantially greater than that of leading taillights, the exposureperiod of the frame in which leading taillights is detected is at leastapproximately ten times the length of the exposure period during whichoncoming headlights are detected. Most preferably, the exposure periodfor detecting leading taillights is approximately 40 times the exposureperiod for detecting oncoming headlights. In the illustrated embodiment,an exposure period of 0.004 seconds is utilized for detecting taillampsand 0.0001 seconds for detecting oncoming headlamps. The exposure periodis the time during which each photosensor element 42 integrates photonsbefore being read and reset by digital signal processor 13 a.Establishing a different exposure period for detecting headlights versestaillights facilitates the use of existing and anticipated sensortechnology by accommodating the dynamic range of such sensor technology.Exposure may also be adaptively established on a priority basis. In onesuch embodiment, exposure is set to a shorter headlight setting. Ifheadlights are detected, the headlights 18 of vehicle 10 are dimmed andthe exposure period is kept short. If no headlights are detected, thenext frame is set to a longer exposure period. This has the advantage ofshorter system cycle time as well as a reduction in sensitivity tosensor saturation and blooming. In another such embodiment, the exposureperiod is initially set to a long period. If an oncoming headlight istentatively detected, the exposure period could then be switched to ashort period to confirm the observation.

Vehicle headlight dimming control 12 carries out a control routine 100(FIGS. 7 a-7 d). At the beginning of each pass through the routine,which occurs for every frame captured by the imaging sensor, a frame isgrabbed at 102 and all of the pixels in the frame are processed asfollows. Counters used for detecting white headlight sources and redtaillight sources are zeroed at 104. It is then determined at 106whether the previously processed frame was for detecting headlights ortaillights. This is determined by looking at a variable “process.tails”which will be set to “yes” if the previous frame was processed to detectheadlights and will be set to “no” if the previous frame was processedto detect taillights. If it is determined at 106 that the variable“process.tails” is set to “yes,” the control proceeds to 108 in order toprocess the next frame to detect taillights. If it is determined at 106that the variable process.tails is set to “no,” then control passes to109 in order to process the next frame as a headlight detecting frame.

The taillight detecting frame process begins at 108 by setting theexposure period for the imaging sensor module to grab the next frameaccording to a headlamp exposure level. In the illustrated embodiment,the exposure period for detecting headlights is set at 0.0001 seconds.Processing of the taillight frame proceeds at 110 by examining, for each“red” pixel, whether the intensity of light sensed by that pixel isgreater than a threshold and whether the intensity of light sensed bythat pixel is greater than a selected number of multiples of theintensity of light sensed by an adjacent “blue” pixel and a selectednumber of multiples of the intensity of light sensed by an adjacent“green” pixel. If so, then a “red” counter is incremented at 114.Preferably, the ratio of red pixel intensity to green or blue pixelintensity is selected as a power of 2 (2, 4, 8, 16 . . . ) in order toease digital processing. However, other ratios may be used and differentratios can be used between red/green and red/blue pixels. In theillustrated embodiment, a ratio of 4 is selected based upon ratiosestablished from CIE illuminant charts known to skilled artisans. Basedupon these charts, a ratio greater than 4 would provide greaterdiscrimination. Such greater discrimination may not be desirable becauseit could result in failure to identify a leading taillight and, thereby,a failure to dim the headlights of the controlled vehicle. After allpixels have been processed, the parameter “process.tails” is set to “no”at 116 and control proceeds to 118 (FIG. 7 c).

In a similar fashion, processing of a headlight frame begins at 110 bysetting the exposure period for the imaging sensor module to grab thenext frame as a red taillight detecting frame. This is accomplished bysetting the exposure period of the imaging sensor module to 0.004seconds. It is then determined at 120 for each pixel whether an adjacentset of “red,” “green,” and “blue” pixels each exceeds a particularthreshold and whether the pixel intensity levels all fall within aparticular range, such as within 20 percent of each other. If all of thered, green, and blue pixels exceed a threshold and pass the ratio test,then it is determined that a white light source is being sensed and a“white” counter is incremented at 122. After all of the pixels in theframe have been processed, the process.tails flag is set to a “yes”state at 124. Control then passes to 118.

It is determined at 118 whether both the “white” and the “red” countersare below respective high-beam thresholds. If so, a high-beam framecounter is incremented and a low-beam frame counter is set to zero at120. If it is determined at 118 that both the “white” and the “red”counters are not less than a threshold, it is then determined at 126whether either the “red” counter or the “white” counter is greater thana respective low-beam threshold. If so, the high-beam frame counter isset to zero and the low-beam frame counter is incremented at 128. If itis determined at 126 that neither the “red” counter or the “white”counter is greater than the respective low-beam threshold, then both thehigh-beam frame counters and the low-beam frame counters are set to zeroat 130.

Control then passes to 132 where it is determined if the low-beam framecounter is greater than a particular threshold. If so, high-beam enablesignal 94 is set to a “low-beam” state at 134. Additionally, thelow-beam frame counter is set to the threshold level. If it isdetermined at 132 that the low-beam frame counter is not greater thanits threshold, it is determined at 136 whether the high-beam framecounter is greater than its threshold. If so, high-beam enable signal 94is set to “high-beam” state at 138 and the high-beam frame counter isreset to its threshold level.

Control routine 100 provides hysteresis by requiring that a headlightspectral signature or a taillight spectral signature be detected for anumber of frames prior to switching the headlights to a low-beam state.Likewise, the absence of a detection of an oncoming headlight or aleading taillight must be made for multiple frames in order to switchfrom a low-beam to a high-beam state. This hysteresis guards againsterroneous detection due to noise in a given frame and eliminatesheadlamp toggling when sources are at the fringe of detection range. Inthe illustrated embodiment, it is expected that a vehicle headlightcontrol system 12 will respond to a change in the state of light sourcesin the forward field of view of the vehicle in less than 0.5 seconds. Anadditional level of hysteresis may be provided by forcing the headlampsto stay in a low-beam state for a given number of seconds after atransition from high beams to low beams. The reverse would not occur;namely, holding a high-beam state for a particular period to avoidannoyance to drivers of oncoming or leading vehicles.

In the illustrated embodiment, red light sources, which have thespectral signature and intensity of taillights, are detected bydetermining that a “red” pixel, namely a pixel which is exposed to lightin the visible red band, is both greater than a given multiple of the“green” and “blue” adjacent pixels, as well as being greater than athreshold and that white light sources, which are the spectralsignatures of headlights, are detected by determining that “red,”“green,” and “blue” pixels are both within a particular intensity rangeof each other as well as being greater than a threshold. Thisdouble-testing helps to reduce false detection of light sources.However, it would be possible to detect red light sources only bylooking at the intensity of “red” pixels and to detect white lightsources by determining that an adjacent set of “red,” “blue,” and“green” pixels are all above a particular threshold.

In the illustrated embodiment, spectral filtering is carried out in amanner which exposes each photosensing element in the photosensor arrayto a band of light falling within one of the primary ranges of thevisible spectrum, namely red, green, or blue as illustrated in FIG. 8 a.However, different bands in the frequency spectrum may be utilizedincluding not only visible spectrum bands but invisible spectrum bandsincluding infrared and ultraviolet bands as illustrated in FIG. 8 b. Theband selection could also be chosen from visible spectral regions thatdo not correspond with the primary spectrums. For example, the spectralfilter may be selected in order to detect at the pixel level red lightsources and the complement of red light sources as illustrated in FIG. 8c. These binary indications could be utilized to detect red taillightsby determining that the “red” pixel is greater than a threshold andgreater than a number of multiples of the intensity sensed by the “redcomplement” pixel adjacent thereto. Likewise, a white light sourceindicative of oncoming headlights could be detected by determining thatboth the “red” pixel and the “red complement” pixel adjacent thereto areboth above a particular threshold and within a particular intensityrange of each other. It may also be desirable to select bands that fallbetween primary spectrum regions or any other bands that may bedesirable for a particular application.

Photosensing array 38 may be a charge couple device (CCD) array of thetype commonly utilized in video camcorders and the like. Alternatively,photosensing array 38 could be a CMOS array of the type manufactured byVLSI Vision Ltd. (VVL) in Edinburgh, Scotland. Additionally, a hybrid ofthe CCD and CMOS technology may be employed. Other potentially usefulphotosensing technologies include CID, MOS, photo diodes, and the like.

In an alternative embodiment, an imaging sensor module 14 b includes twoor more pairs of photosensor arrays 38 b (FIG. 6). Each photosensorarray 38 b has an associated spectral filter array 40 b and opticaldevice 36 b. In this embodiment, each array 38 b is operated by digitalsignal processor 58 b to have an exposure period that is set fordetecting either oncoming headlights or leading taillights. In thismanner, each frame of the scene captured by each array is utilized todetect a particular light source. This is in contrast to light-sensingmodule 14 a in FIG. 5 in which each light source is detected inalternating frames. Each spectral filter 40 b is identical, whereby eacharray 38 b is capable of detecting light sources having spectrumcomposition including red, green, and blue regions of the spectrum.However, the spectral filters may be custom configured to the particularapplication. This may result in a homogeneous composition or a morecomplex mosaic, especially where light sources are examined in three ormore spectral regions.

In yet an additional single lens system embodiment, an imaging sensormodule 14 c includes three light-sensing arrays (not shown) and aspectral separation device overlying the light-sensing arrays whichdirects spectral bands to different arrays (FIG. 9). An example of suchspectral separation device is a refracting optical splitter, such asdichroic mirrors or prisms. In this manner, each light-sensing arraydetects light in either the red or green or blue region of the spectrum.As such, imaging sensor module 14 c produces three output signals on aline 64, each representing detected light in one of the red or green orblue spectral regions. The output signals on line 64 includeframe-timing signals which are decoded by digital acquisition circuits66 which produces a digital output signal 68′ indicative of intensitylevels of adjacent red, green, and blue pixels. Digital acquisitioncircuit 66 additionally produces a timing signal output 70 which isutilized by a detection control circuit 72 in order to supplysynchronizing signals, at 74, to imaging sensor module 14 c and digitalacquisition circuit 66. A control and timing signal 86 is produced bydigital acquisition circuit 66 and supplied to detection circuits 76 and78 and ambient detection circuit 84 in order to enable the circuits todistinguish between subsequent frames captured by the light-sensingmodules. As with previously described embodiments, digital output signal68′ is supplied to taillight detection circuit 76, headlight detectioncircuit 78, and ambient sense logic circuit 84.

The present invention is capable of identifying point sources of lightin any particular location within the scene viewed forward of thevehicle. Additional discrimination between oncoming headlights andleading taillights may be accomplished by taking into account therelative location of the source of light within the scene. For example,as best seen by reference to FIG. 11 a, particular relationships havebeen discovered to exist between light sources of interest and theirspatial location forward of the vehicle. Oncoming headlights and leadingtaillights of interest can be characterized, at least in part, basedupon their displacement from the central axis of the vehicle. On-axislight sources of interest can be at both close and far away separationdistances. However, off-axis light sources may only be of interest if ata close separation distance from the vehicle. Assuming for illustrationpurposes that headlights and taillights are of the same size, headlightsand taillights of interest occupy an increasing spatial area as theymove off axis. Therefore, the resolution required to detect lights ofinterest may decrease off axis. Additionally, the fact that close-upoff-axis light sources have significant spatial area would allowimage-processing techniques to be employed to discriminate betweenclose-up off-axis light sources of interest and distant off-axis lightsources, which are not of interest. This may be accomplished throughcustomized optics or other known variations in pixel resolution.Furthermore, headlights and taillights of interest are of greaterintensity, because of their closeness, off axis. This allows an increasein intensity detection thresholds off axis without missing detection ofsuch light sources. This increase in detection threshold and reductionin resolution off axis assists in avoiding false detection of lightsources not of interest, such as a streetlights, building lights, andthe like.

In order to take into account this spatial differentiation, the presentinvention comprehends detecting light sources at a lower thresholdcentrally of the scene and at a higher threshold at the periphery of thescene. This may be accomplished either optically, or electronically, orboth. Optically, this may be accomplished by providing a non-uniformmagnification to optical device 36. For example, an optical device mayhave optical magnification at a central portion thereof and an opticalattenuation at a peripheral region thereof. Additionally, optical device36 may have a relatively wide horizontal field of view and a relativelynarrow vertical field of view. The narrow vertical field of view wouldtend to reduce the detection of street lights and other overhead lightsources. In a preferred embodiment, optical device 36 is a lens that ismade from injection-molded plastic. Electronically, such spatialdifferentiation may be accomplished by establishing a higher thresholdlevel for pixel intensity detection for pixels located at the peripheryof the scene than for pixels located centrally of the scene. This wouldcause centrally positioned light sources to be detected at a lowerintensity level than sources detected at the periphery of the scene.Such spatial differentiation could also be accomplished by anon-symmetrical mapping of light to the sensor array, as illustrated inFIG. 11 b, or by masking portions 98 a, 98 b, and 98 c, at the peripheryof the scene, as illustrated in FIG. 11 c, so that these portions arenot sensed at all. Spatial differentiation could also be accomplished byproviding non-uniform pixel size.

The present invention is exceptionally sensitive to sources of lighthaving spectral signatures of oncoming headlights and leadingtaillights. By recognizing the spectral signature of the light sources,many non-relevant light sources may be ignored. By examining lightsources pixel-by-pixel, relatively small light sources may be detectedat great distances in order to dim the headlights well before theybecome a nuisance to the driver of the vehicle ahead of the controlvehicle. This is accomplished, according to a preferred embodiment, byutilizing an imaging sensor made up of an array of photosensing elementsin a compact design which responds to light sources in a scene forwardof the vehicle. Furthermore, such sensor preferably utilizes digitalprocessing techniques which are well adapted for use with custom digitalelectronic circuitry, avoiding the expense and speed constraints ofgeneral purpose programmable microprocessors.

The present invention takes advantage of the spectral signatures both oflight sources which must be detected in a headlight dimming control aswell as the spectral signatures of light sources which must be rejectedin a headlight dimming control. For example, federal regulationsestablish specific spectral bands that must be utilized in vehicletaillights; namely red. Furthermore, federal legislation prohibits theuse of red light sources in the vicinity of a highway. Lane markers,signs, and other sources of reflected light are all specified in amanner which may be readily identified by spectral signature. Oncomingheadlights, according to known technology, have a visible spectralsignature which is predominantly white light. As light source technologyevolves, the present invention facilitates detection of other spectralsignatures of light sources in the future.

The present invention is capable of utilizing spatial filtering to evenfurther enhance the ability to identify light sources. By spatialfiltering is meant consideration of not only whether a particular pixel,or pixel group, is detecting a light source having a particular spectralsignature, but also what adjacent, or closely related, pixels or pixelgroups, are detecting. For example, it can be concluded that veryclosely adjacent red and white light sources are not of interest asoncoming headlights or taillights. An example where such pattern couldbe observed is a streetlight observed with a system having imperfectcolor correction, which can produce a white light surrounded by a redhalo. By evaluation of adjacent pixel groups, a closely proximate redlight source and white light source can be identified as a streetlightand not either a headlight or a taillight.

Pattern recognition may be used to further assist in the detection ofheadlights, taillights, and other objects of interest. Patternrecognition identifies objects of interest based upon their shape,reflectivity, luminance, and spectral characteristics. For example, thefact that headlights and taillights usually occur in pairs could be usedto assist in qualifying or disqualifying objects as headlights andtaillights. By looking for a triad pattern, including the centerhigh-mounted stoplight required on the rear of vehicles, stoplightrecognition can be enhanced. Furthermore, object recognition can beenhanced by comparing identified objects over successive frames. Thistemporal processing can yield information on object motion and can beused to assist in qualifying or disqualifying objects of interest.

Spatial filtering can also be useful in identifying atmosphericconditions by detecting effects on light sources caused by particulartypes of atmospheric conditions. One such atmospheric condition is fog.A bright light source 102 is surrounded by a transition region 104between the intensity of the light source and the black background (FIG.12 a). Fog, or fine rain, tends to produce a dispersion effect aroundlight sources which causes a series of transition regions 104 a, 104 b .. . 104 n which extend further from the light source (FIG. 12 b). Byplacing appropriate limits on the size of the transition region, fog orlight rain, or a mixture of both, or other related atmosphericconditions, can be detected. In response to such atmospheric conditions,vehicle headlight dimming control 12 may activate fog lights, inhibitswitching to high beams, or perform other control functions.Furthermore, fog, or fine rain, can be detected, or confirmed, byanalyzing the effects of headlights 18 in the forward scene as reflectedoff of moisture particles.

Spatial filtering can also be used to detect rain on windshield 32. Thismay be accomplished by performing statistical analyses between a pixel,or pixel group, and adjacent pixels or pixel groups. A view forward of avehicle through a dry windshield would be sensed by an imaging sensormodule as continuously varying differences between adjacent pixels, orpixel groups, assumed to be under constant illumination from lightsources. When, however, a droplet of water or a snowflake is onwindshield 32, an effect is created which causes a lack of continuousvariation of differences between adjacent pixels, or pixel groups. Thishas the tendency to reduce the first derivative of the pixel, acondition which can be determined by processing.

Processing can be used to determine the first derivative of an imagecaptured by image-sensing module 14 by determining a measure of theentropy, or disarray, of a pixel, or pixel group, with respect to itsneighbors. For example, an approximation of the first derivative for apixel is: where N=8 and where Pi is a given pixel and Pj is one of 8neighboring pixels.

$\frac{\mathbb{d}\left( P_{i} \right)}{\mathbb{d}{xy}} = \frac{\sqrt{\sum\limits_{j = 1}^{n}}\left( {{Pi} - {Pj}} \right)^{2}}{N}$

It should be apparent to those skilled in the art that the invention iscapable of performing control functions other than controlling thedimming of the vehicle's headlights. For example, spectral signatureidentifications may be utilized to detect the state of a traffic lightto either warn the driver that a light has changed from green to yellowto red or to automatically decelerate and stop the vehicle. Also, bysensing that the intensity of a leading taillight has abruptlyincreased, a condition where the leading vehicle is braking may beidentified and suitable action taken.

The invention may be utilized to identify particular traffic signs bytheir spectral signature as well as their geometric organization. Forexample, red octagons may be identified as stop signs, yellow trianglesas caution signs, and the like. These capabilities are a result of thepresent invention providing a significant reduction in the amount ofdata to be processed because the image forward of the vehicle iscaptured in a manner which preselects data. Preselection of data isaccomplished by configuring the sensor array, including the opticsthereof, to consider the spatial, as well as the spectral,characteristics of light sources.

The present invention may be used to determine the environment in whichthe vehicle is operated. For example, a high level of “non-qualified”light sources; namely, light sources that are not headlights ortaillights, as well as “qualified” light sources can be used todetermine a measurement of the activity level around the vehicle;namely, that the vehicle is in an urban environment which may be auseful input for particular control algorithms. This may be accomplishedas follows. An activity counter is established which represents a totalnumber of pixels, or pixel groups, whose red, green, or blue componentsexceed a threshold. The threshold is set to a relatively low value,namely just above the noise floor. This counter, which registers anyreal detected source, is reset and retabulated every frame, preferablyduring the exposure period for detecting taillights. If the activitycounter exceeds a particular value, then a high activity environment isdetected. One use of this information would be to inhibit the controlfrom switching the vehicle's headlights from a low-beam state to ahigh-beam state unless a low activity condition exists for awhile. Theactivity counter may be used by the control in combination with alow-beam duration counter which records the number of frames that thesystem has been in a low-beam state. It is reset upon system power-upand at every transition from the high-to-low beam states. The controlmay be inhibited from switching the vehicle's headlights to thehigh-beam state unless either the low-beam duration counter exceeds avalue or the activity counter indicates a sustained low activitycondition.

The present invention can be used to detect lane markers in order toeither assist in steering the vehicle or provide a warning to the driverthat a lane change is occurring. The capability of the invention todetect rain on the vehicle's windshield could be used to control thevehicle's wipers both between OFF and ON conditions and to establish afrequency of intermittent operation.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the inventionwhich is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An image sensing systemfor a vehicle, said image sensing system comprising: an imagercomprising a two-dimensional CMOS photosensor array of light sensingphotosensor elements; wherein said imager is disposed at or proximate toan in-cabin portion of a windshield of a vehicle equipped with saidimage sensing system, and wherein said imager has a forward field ofview to the exterior of the equipped vehicle through the windshield ofthe equipped vehicle; wherein said photosensor array is operable tocapture image data; a control comprising an image processor; whereinsaid image sensing system identifies objects in said forward field ofview of said imager via processing of captured image data by said imageprocessor; wherein said image sensing system is operable to identify atleast one of (i) approaching headlights, (ii) leading taillights, (iii)lane markers, (iv) traffic signs, (v) traffic lights, (vi) stop signsand (vii) caution signs; wherein said photosensor array is operable tocapture frames of image data; and wherein said image sensing systemincludes an exposure control which determines an accumulation period oftime that said photosensor array senses light when capturing a frame ofimage data.
 2. The image sensing system of claim 1, wherein said imagerhas a forward field of view to the exterior of the equipped vehiclethrough the windshield of the equipped vehicle at a region of thewindshield that is swept by a windshield wiper of the equipped vehicle.3. The image sensing system of claim 1, wherein said exposure controldetermines a plurality of accumulation periods of time that saidphotosensor array senses light when capturing frames of image data. 4.The image sensing system of claim 3, wherein said plurality ofaccumulation periods comprises a first accumulation period for a firstframe of captured image data and a second accumulation period for asecond frame of captured image data and wherein said first accumulationperiod is a longer time period than said second accumulation period. 5.The image sensing system of claim 4, wherein said second frame ofcaptured image data is the next frame that immediately follows captureby said photosensor array of said first frame of captured image data. 6.The image sensing system of claim 4, wherein said first frame is usedwhen detecting leading vehicle taillights.
 7. The image sensing systemof claim 4, wherein said second frame is used when detecting approachingvehicle headlights.
 8. The image sensing system of claim 1, wherein saidexposure control is adaptive.
 9. The image sensing system of claim 8,wherein an accumulation period for a frame of captured image data is seton a priority basis.
 10. The image sensing system of claim 8, wherein anaccumulation period for a frame of captured image data is determined inresponse to what said image sensing system is sensing to be present inthe forward field of view of said imager.
 11. The image sensing systemof claim 10, wherein what said image sensing system is sensing to bepresent in the forward field of view of said imager comprises at leastone of (a) a headlight of an approaching vehicle and (b) a taillight ofa leading vehicle.
 12. The image sensing system of claim 1, wherein saidexposure control operates to mitigate at least one of (i) saturation ofphotosensor elements of said photosensor array and (ii) blooming. 13.The image sensing system of claim 1, wherein said exposure controlmaintains an accumulation period until an object of interest is at leasttentatively detected.
 14. The image sensing system of claim 13, whereinsaid exposure control changes to a different accumulation period when anobject of interest is at least tentatively detected.
 15. The imagesensing system of claim 14, wherein said object of interest comprises aheadlight of an approaching vehicle.
 16. The image sensing system ofclaim 15, wherein said exposure control changes to a shorteraccumulation period when a headlight of an approaching vehicle is atleast tentatively detected.
 17. The image sensing system of claim 1,wherein said photosensor array of light sensing photosensor elements isoperated by a digital signal processor to have said accumulation period.18. The image sensing system of claim 1, wherein said photosensor arrayof light sensing photosensor elements comprises at least 262,144photosensor elements.
 19. The image sensing system of claim 1, whereinsaid imager comprises a spectral filter that substantially attenuateslight having a wavelength greater than about 830 nanometers and whereinlight emitted by sources external of the equipped vehicle and/orreflected by objects external of the equipped vehicle passes through,and is filtered by, said spectral filter to be incident on at least someof said light sensing photosensor elements of said photosensor array.20. The image sensing system of claim 1 comprising a spectral filter,wherein light emitted by sources external of the equipped vehicle and/orreflected by objects external of the equipped vehicle passes through,and is filtered by, said spectral filter to be incident on at least someof said light sensing photosensor elements of said photosensor array.21. The image sensing system of claim 20, wherein said spectral filtercomprises a red filter that passes visible light of wavelength generallyin the red portion of the visible spectrum and that substantiallyattenuates light having wavelengths generally outside the red portion ofthe visible spectrum.
 22. The image sensing system of claim 20, whereinsaid spectral filter comprises a red complement filter thatsubstantially passes wavelengths generally outside the red portion ofthe visible spectrum and that substantially attenuates wavelengthsgenerally in the red portion of the visible spectrum.
 23. The imagesensing system of claim 20, wherein said imager comprises a lens. 24.The image sensing system of claim 23, wherein said photosensor array oflight sensing photosensor elements, said lens and said spectral filterare housed within an imager module.
 25. The image sensing system ofclaim 24, wherein said imager module is housed in a housing that mountsvia a bracket to the vehicle windshield.
 26. The image sensing system ofclaim 25, wherein said bracket also mounts an interior rearview minor.27. The image sensing system of claim 23, wherein said spectral filteris disposed between said lens and said photosensor array of lightsensing photosensor elements.
 28. The image sensing system of claim 1,wherein said imager comprises a lens.
 29. The image sensing system ofclaim 28, wherein a spectral filter is disposed between said lens andsaid photosensor array of light sensing photosensor elements.
 30. Theimage sensing system of claim 1, wherein said imager is disposed at awindshield electronics module and wherein said windshield electronicsmodule comprises a housing that mounts via a bracket to the windshieldof the equipped vehicle.
 31. The image sensing system of claim 30,wherein said bracket also mounts an interior rearview minor.
 32. Theimage sensing system of claim 1, wherein at least one of (a) saidphotosensor array of light sensing photosensor elements comprises anarray of rows and columns and wherein at least one of (i) the number ofcolumns exceeds 512, (ii) the number of rows exceeds 512 and (iii) saidphotosensor array of light sensing photosensor elements comprises atleast 262,144 photosensor elements, (b) said image sensing systemprocesses said image data to identify objects based, at least in part,on at least one of (i) spatial differentiation and (ii) spectralcharacteristic, and (c) identification of objects is enhanced bycomparing image data of objects over successive frames of captured imagedata.
 33. The image sensing system of claim 1, wherein identification ofobjects is based at least in part on a spectral characteristic ofobjects present in said forward field of view, and whereinidentification of objects is based at least in part on said controldetermining that spatially adjacent regions of said forward field ofview include objects having a particular spectral characteristic. 34.The image sensing system of claim 1, wherein, at least in partresponsive to image processing of captured image data by said imageprocessor, said control determines if a particular object presentforward of the equipped vehicle has a particular spectral characteristicby comparing levels of light sensed by photosensor elements whichrespond to light in a particular spectral region with levels of lightsensed by photosensor elements which respond to light in a differentspectral region, and wherein said object present forward of the equippedvehicle comprises one of (i) an approaching headlight, (ii) a leadingtaillight, (iii) a lane marker, (iv) a traffic sign, (v) a trafficlight, (vi) a stop sign and (vii) a caution sign.
 35. The image sensingsystem of claim 1, wherein a red spectral filter is disposed at some ofsaid light sensing photosensor elements and a red spectral filter is notdisposed at others of said light sensing photosensor elements.
 36. Theimage sensing system of claim 35, wherein at least one of (a) saidothers of said light sensing photosensor elements are neighbors of saidred filtered light sensing photosensor elements, and (b) said others ofsaid light sensing photosensor elements are immediately adjacent to saidred filtered light sensing photosensor elements.
 37. The image sensingsystem of claim 1, wherein at least one of (a) said image sensing systemdetermines an activity level at the equipped vehicle, (b) said imagesensing system determines an environment in which the equipped vehicleis being driven, and (c) said image sensing system determines anenvironment in which the equipped vehicle is being driven and said imagesensing system controls a headlight of the equipped vehicle at least inpart responsive to said determination of the environment in which theequipped vehicle is being driven.
 38. The image sensing system of claim1, wherein, at least in part responsive to image processing of capturedimage data by said image processor, said image sensing system isoperable to identify lane markers on a road being traveled by theequipped vehicle in order to at least one of (a) assist the driver insteering the equipped vehicle and (b) provide a warning to the driver ofthe equipped vehicle, and wherein identification of lane markers, atleast in part, comprises identification of lane markers by a spectralcharacteristic.
 39. The image sensing system of claim 1, whereinidentification of objects is based at least in part on at least one of(i) shape, (ii) luminance, (iii) geometry, (iv) spatial location, (v)motion and (vi) spectral characteristic.
 40. The image sensing system ofclaim 1, wherein, at least in part responsive to image processing ofcaptured image data by said image processor, said image sensing systemis operable to identify traffic signs and wherein said image sensingsystem is operable to identify traffic signs by at least one of (a) aspectral characteristic of the traffic signs and (b) a geometricorganization of the traffic signs.
 41. The image sensing system of claim1, wherein, at least in part responsive to image processing of capturedimage data by said image processor, said image sensing system isoperable to determine that at least one of rain, fog and mist is presentin said forward field of view.
 42. The image sensing system of claim 1,wherein said control controls a headlight of the equipped vehicleresponsive to identification of at least one of (i) a headlight of anapproaching vehicle in said forward field of view and (ii) a taillightof a leading vehicle in said forward field of view, and wherein saidcontrol is operable to at least one of (a) adjust an aim of theheadlight of the equipped vehicle, (b) adjust an intensity of theheadlight of the equipped vehicle, (c) adjust a beam pattern of theheadlight of the equipped vehicle and (d) switch between a daytimerunning light beam condition and a different beam condition.
 43. Theimage sensing system of claim 1, wherein said control, at least in partresponsive to processing of captured image data by said image processor,is operable to determine an ambient light level at the equipped vehicle,and wherein said control determines the ambient light level byprocessing image data captured by a subset of said light sensingphotosensor elements over a period of time.
 44. The image sensing systemof claim 1, wherein, at least in part responsive to processing ofcaptured image data by said image processor, said control at least oneof (a) controls a headlight of the equipped vehicle at least in part asa function of the speed of the equipped vehicle, (b) controls aheadlight of the equipped vehicle, (c) controls a speed of the equippedvehicle and (d) generates an alert to the driver of the equippedvehicle.
 45. The image sensing system of claim 1, wherein, at least inpart responsive to processing of captured image data by said imageprocessor, said control at least one of (i) warns the driver of theequipped vehicle, (ii) decelerates the equipped vehicle and (iii) stopsthe equipped vehicle.
 46. The image sensing system of claim 1, whereinsaid image sensing system is operable to detect the state of a trafficlight, and wherein, at least in part responsive to processing ofcaptured image data by said image processor, said control detects thecolor state of said traffic light and said control at least one of (i)warns the driver of the equipped vehicle, (ii) decelerates the equippedvehicle and (iii) stops the equipped vehicle, and wherein said imageprocessor detects the color state of said traffic light changing from atleast one of (a) green to yellow and (b) yellow to red.
 47. The imagesensing system of claim 1, wherein at least one of (a) image processingof captured image data by said image processor comprises determinationthat an object present forward of the equipped vehicle is a stop signbased upon at least one of (i) the object comprising an octagon shape,(ii) the object comprising a red color and (iii) the spatial location ofthe object in the field of view of said imager, and (b) image processingof captured image data by said image processor comprises determinationthat an object present forward of the equipped vehicle is a caution signbased upon at least one of (i) the object comprising a triangular shape,(ii) the object comprising a yellow color and (iii) the spatial locationof the object in the field of view of said imager.
 48. The image sensingsystem of claim 1, wherein said imager is accommodated in a body at thein-cabin portion of the windshield of the equipped vehicle.
 49. An imagesensing system for a vehicle, said image sensing system comprising: animager comprising a two-dimensional CMOS photosensor array of lightsensing photosensor elements; wherein said imager is disposed at orproximate to an in-cabin portion of a windshield of a vehicle equippedwith said image sensing system, and wherein said imager has a forwardfield of view to the exterior of the equipped vehicle through thewindshield of the equipped vehicle; wherein said photosensor array isoperable to capture image data; a control comprising an image processor;wherein said image sensing system identifies objects in said forwardfield of view of said imager via processing of captured image data bysaid image processor; wherein identification of objects is based atleast in part on at least one of (i) shape, (ii) luminance, (iii)geometry, (iv) spatial location, (v) motion and (vi) spectralcharacteristic; wherein objects identified by said image sensing systemcomprise at least one of (i) headlights of approaching vehicles, (ii)taillights of leading vehicles, (iii) lane markers on a road beingtraveled by the equipped vehicle, (iv) traffic signs, (v) trafficlights, (vi) stop signs and (vii) caution signs; wherein saidphotosensor array is operable to capture frames of image data; whereinsaid image sensing system includes an exposure control which determinesan accumulation period of time that said photosensor array senses lightwhen capturing a frame of image data; and wherein, responsive at leastin part to image processing of captured image data by said imageprocessor, said control at least one of (a) controls a headlight of theequipped vehicle, (b) controls a headlight of the equipped vehicle as afunction of a speed of the equipped vehicle, (c) controls a speed of theequipped vehicle, (d) generates an alert to the driver of the equippedvehicle, (e) warns the driver of the equipped vehicle, (f) deceleratesthe equipped vehicle, (g) stops the equipped vehicle, (h) determines anambient light level at the equipped vehicle, (i) activates a fog lightof the equipped vehicle, (j) adjusts a light beam emitted by a headlightof the equipped vehicle, (k) inhibits operation of a headlight of theequipped vehicle in a high beam state, (l) assists the driver insteering the equipped vehicle, (m) adjusts an aim of a headlight of theequipped vehicle, (n) adjusts an intensity of a headlight of theequipped vehicle, (o) adjusts a beam pattern of a headlight of theequipped vehicle, (p) switches between a first lighting condition and asecond lighting condition, (q) discriminates headlights of approachingvehicles from streetlights, (r) discriminates taillights of leadingvehicles from streetlights, (s) discriminates headlights of approachingvehicles from reflections off signs of light emitted by a headlight ofthe equipped vehicle, (t) discriminates taillights of leading vehiclesfrom reflections off signs of light emitted by a headlight of theequipped vehicle, and (u) determines at least one of fog, rain and mistin said forward field of view.
 50. The image sensing system of claim 49,wherein said imager has a forward field of view to the exterior of theequipped vehicle through the windshield of the equipped vehicle at aregion of the windshield that is swept by a windshield wiper of theequipped vehicle.
 51. The image sensing system of claim 49, wherein ared spectral filter is disposed at some of said light sensingphotosensor elements and wherein a red spectral filter is not disposedat others of said light sensing photosensor elements.
 52. The imagesensing system of claim 51, wherein said imager comprises a lens. 53.The image sensing system of claim 52, wherein said red spectral filteris disposed between said lens and said photosensor array of lightsensing photosensor elements.
 54. The image sensing system of claim 52,wherein said photosensor array of light sensing photosensor elements,said lens and said red spectral filter are housed within an imagermodule, and wherein said imager module is housed in a housing thatmounts via a bracket to the vehicle windshield.
 55. The image sensingsystem of claim 54, wherein at least one of (a) said exposure controldetermines a plurality of accumulation periods of time that saidphotosensor array senses light when capturing frames of image data, (b)said exposure control determines a plurality of accumulation periods oftime that said photosensor array senses light when capturing frames ofimage data and wherein said plurality of accumulation periods comprisesa first accumulation period for a first frame of captured image data anda second accumulation period for a second frame of captured image dataand wherein said first accumulation period is a longer time period thansaid second accumulation period, (c) said exposure control determines aplurality of accumulation periods of time that said photosensor arraysenses light when capturing frames of image data and wherein saidplurality of accumulation periods comprises a first accumulation periodfor a first frame of captured image data and a second accumulationperiod for a second frame of captured image data and wherein said firstaccumulation period is a longer time period than said secondaccumulation period and wherein said first frame is used when detectingleading vehicle taillights and said second frame is used when detectingapproaching vehicle headlights, (d) said exposure control is adaptiveand wherein at least one of (i) an accumulation period for a frame ofcaptured image data is set on a priority basis and (ii) an accumulationperiod for a frame of captured image data is determined in response towhat said image sensing system is sensing to be present in the forwardfield of view of said imager, and (e) said exposure control maintains anaccumulation period until an object of interest is at least tentativelydetected and wherein said exposure control changes to a differentaccumulation period when an object of interest is at least tentativelydetected.
 56. The image sensing system of claim 55, wherein at least oneof (a) at least a portion of said control is commonly formed with saidphotosensor array of light sensing photosensor elements on asemiconductor substrate, (b) said control comprises a logic circuit andat least a portion of said logic circuit is commonly formed with saidphotosensor array of light sensing photosensor elements on asemiconductor substrate, (c) said control comprises a logic circuit andat least a portion of said logic circuit comprises digital logicelements commonly formed with said photosensor array of light sensingphotosensor elements on a semiconductor substrate, and (d) at least oneof (i) a central processing unit, (ii) read-only-memory, (iii) ananalog-to-digital converter, (iv) a logic circuit, (iv) a clock, (v)random access memory and (vi) a digital-to-analog converter is commonlyformed with said photosensor array of light sensing photosensor elementson a semiconductor substrate.
 57. The image sensing system of claim 56,wherein said photosensor array of light sensing photosensor elementscomprises at least 262,144 photosensor elements.
 58. The image sensingsystem of claim 49, wherein said control, responsive at least in part toprocessing of captured image data by said image processor, generates atleast one control output for controlling a headlight of the equippedvehicle.
 59. The image sensing system of claim 58, wherein said imagercomprises a lens, and wherein light incident on said imager includes, atleast in part, light output by the headlight of the equipped vehiclethat is scattered by at least one of fog, snow and rain that is presentin the field of view of said imager exterior and forward of the equippedvehicle, and wherein said image sensing system recognizes scattering oflight output by the headlight of the equipped vehicle and wherein,responsive to recognition of scattering of light exterior and forward ofthe equipped vehicle, said control at least one of (a) selects anappropriate lighting configuration for the headlight of the equippedvehicle, (b) activates a fog light of the equipped vehicle, (c) adjustsa light beam emitted by the headlight of the equipped vehicle and (d)inhibits operation of the headlight of the equipped vehicle in a highbeam state.
 60. The image sensing system of claim 58, wherein capturedimage data is processed by said image processor to determine if at leastone approaching or leading other vehicle is within a glare area forlight emitted by the headlight of the equipped vehicle and if at leastone approaching or leading other vehicle is within the glare area, theillumination range of the headlight of the equipped vehicle is reduced.61. The image sensing system of claim 58, wherein manual operation ofthe headlight of the equipped vehicle remains functional.
 62. The imagesensing system of claim 49, wherein said image processor processescaptured image data on a frame by frame basis and examines multipleframes in order to detect motion relative to the equipped vehicle oflight sources that are external to the equipped vehicle.
 63. The imagesensing system of claim 62, wherein at least one of (a) said imageprocessor compares multiple frames of captured data to detect verticalmotion of said light sources relative to the equipped vehicle, (b) saidlight sources are overhead street lamps, (c) said image processorcompares multiple frames of captured data to detect horizontal motion ofsaid light sources relative to the equipped vehicle, and (d) said lightsources are light reflected from reflectors.
 64. The image sensingsystem of claim 49, wherein said imager is supported by a mountingstructure that is adapted for attachment at the vehicle windshield so asto physically position said imager within the interior cabin of theequipped vehicle.
 65. The image sensing system of claim 49, wherein saidimager comprises a lens and wherein said lens is at least one of (i)bonded to said photosensor array and (ii) is close to said photosensorarray.
 66. The image sensing system of claim 49, wherein said imager isaccommodated in a body at the in-cabin portion of the windshield of theequipped vehicle.
 67. The image sensing system of claim 49, wherein,responsive at least in part to image processing of captured image databy said image processor, said control switches between a first lightingcondition and a second lighting condition.
 68. The image sensing systemof claim 67, wherein said first lighting condition comprises a daytimerunning light beam condition and said second lighting conditioncomprises a different beam condition.
 69. An image sensing system for avehicle, said image sensing system comprising: an imager comprising atwo-dimensional CMOS photosensor array of light sensing photosensorelements; wherein said imager is disposed at or proximate to an in-cabinportion of a windshield of a vehicle equipped with said image sensingsystem, and wherein said imager has a forward field of view to theexterior of the equipped vehicle through the windshield of the equippedvehicle; wherein said photosensor array is operable to capture imagedata; a control comprising an image processor; wherein said imagesensing system identifies objects in said forward field of view of saidimager via processing of captured image data by said image processor;and wherein at least one of (a) identification of objects is based atleast in part on the spatial location of objects present in said forwardfield of view, (b) said image sensing system determines an activitylevel at the equipped vehicle, (c) said image sensing system determinesan environment in which the equipped vehicle is being driven, (d) saidimage sensing system determines an environment in which the equippedvehicle is being driven and said image sensing system controls aheadlight of the equipped vehicle at least in part responsive to saiddetermination of the environment in which the equipped vehicle is beingdriven and (e) responsive at least in part to image processing by saidimage processor, said control at least one of (i) warns the driver ofthe equipped vehicle, (ii) decelerates the equipped vehicle and (iii)stops the equipped vehicle.
 70. The image sensing system of claim 69,wherein said imager has a forward field of view to the exterior of theequipped vehicle through the windshield of the equipped vehicle at aregion of the windshield that is swept by a windshield wiper of theequipped vehicle.
 71. The image sensing system of claim 69, wherein, atleast in part responsive to image processing of captured image data bysaid image processor, said image sensing system identifies at least oneof (i) headlights of approaching vehicles, (ii) taillights of leadingvehicles and (iii) lane markers on a road being traveled by the equippedvehicle.
 72. The image sensing system of claim 69, wherein at least oneof (a) a spectral filter is disposed at some of said light sensingphotosensor elements and that spectral filter is not disposed at othersof said light sensing photosensor elements, (b) said photosensor arrayof light sensing photosensor elements comprises at least 262,144photosensor elements, (c) a red spectral filter is disposed at some ofsaid light sensing photosensor elements and a red spectral filter is notdisposed at others of said light sensing photosensor elements, (d) a redspectral filter is disposed at some of said light sensing photosensorelements and a red spectral filter is not disposed at others of saidlight sensing photosensor elements and said others of said light sensingphotosensor elements are neighbors of said red filtered light sensingphotosensor elements, and (e) a red spectral filter is disposed at someof said light sensing photosensor elements and a red spectral filter isnot disposed at others of said light sensing photosensor elements andsaid others of said light sensing photosensor elements are immediatelyadjacent to said red filtered light sensing photosensor elements. 73.The image sensing system of claim 69, wherein, at least in partresponsive to image processing of captured image data by said imageprocessor, at least one of (i) said image sensing system is operable toidentify lane markers on a road being traveled by the equipped vehiclein order to at least one of (a) assist the driver in steering theequipped vehicle and (b) provide a warning to the driver of the equippedvehicle and (ii) said image sensing system is operable to identify lanemarkers on a road being traveled by the equipped vehicle and whereinidentification of lane markers comprises identification of lane markersby a spectral characteristic.
 74. The image sensing system of claim 69,wherein said image sensing system includes an exposure control whichdetermines an accumulation period of time that said photosensor arraysenses light when capturing a frame of image data and wherein at leastone of (a) said exposure control determines a plurality of accumulationperiods of time that said photosensor array senses light when capturingframes of image data, (b) said exposure control determines a pluralityof accumulation periods of time that said photosensor array senses lightwhen capturing frames of image data and wherein said plurality ofaccumulation periods comprises a first accumulation period for a firstframe of captured image data and a second accumulation period for asecond frame of captured image data and wherein said first accumulationperiod is a longer time period than said second accumulation period, (c)said exposure control determines a plurality of accumulation periods oftime that said photosensor array senses light when capturing frames ofimage data and wherein said plurality of accumulation periods comprisesa first accumulation period for a first frame of captured image data anda second accumulation period for a second frame of captured image dataand wherein said first accumulation period is a longer time period thansaid second accumulation period and wherein said first frame is usedwhen detecting leading vehicle taillights and said second frame is usedwhen detecting approaching vehicle headlights, (d) said exposure controlis adaptive and wherein at least one of (i) an accumulation period for aframe of captured image data is set on a priority basis and (ii) anaccumulation period for a frame of captured image data is determined inresponse to what said image sensing system is sensing to be present inthe forward field of view of said imager, and (e) said exposure controlmaintains an accumulation period until an object of interest is at leasttentatively detected and wherein said exposure control changes to adifferent accumulation period when an object of interest is at leasttentatively detected.
 75. The image sensing system of claim 69, whereinat least one of (a) at least a portion of said control is commonlyformed with said photosensor array of light sensing photosensor elementson a semiconductor substrate, (b) said control comprises a logic circuitand at least a portion of said logic circuit is commonly formed withsaid photosensor array of light sensing photosensor elements on asemiconductor substrate, (c) said control comprises a logic circuit andat least a portion of said logic circuit comprises digital logicelements commonly formed with said photosensor array of light sensingphotosensor elements on a semiconductor substrate, and (d) at least oneof (i) a central processing unit, (ii) read-only-memory, (iii) ananalog-to-digital converter, (iv) a logic circuit, (iv) a clock, (v)random access memory and (vi) a digital-to-analog converter is commonlyformed with said photosensor array of light sensing photosensor elementson a semiconductor substrate.
 76. The image sensing system of claim 69,wherein said photosensor array of light sensing photosensor elementscomprises an array of rows and columns and wherein at least one of (i)the number of columns exceeds 512, (ii) the number of rows exceeds 512and (iii) said photosensor array of light sensing photosensor elementscomprises at least 262,144 photosensor elements.
 77. The image sensingsystem of claim 69, wherein said imager comprises a lens and whereinsaid photosensor array of light sensing photosensor elements, said lensand a spectral filter are housed within an imager module, and whereinsaid imager module is housed in a housing that mounts via a bracket tothe vehicle windshield.
 78. The image sensing system of claim 69,wherein, at least in part responsive to image processing of capturedimage data by said image processor, at least one of (a) objects presentin said forward field of view are qualified based, at least in part, onobject motion in said forward field of view of said imager, (b) objectspresent in said forward field of view are disqualified based, at leastin part, on object motion in said forward field of view of said imager,(c) said image sensing system determines an activity level at theequipped vehicle, and (d) said image sensing system determines anenvironment in which the equipped vehicle is being driven and controls aheadlight of the equipped vehicle at least in part responsive to saiddetermination of the environment in which the equipped vehicle is beingdriven.
 79. The image sensing system of claim 69, wherein at least oneof (a) image processing of captured image data by said image processorcomprises determination that an object present forward of the equippedvehicle is a stop sign based upon at least one of (i) the objectcomprising an octagon shape, (ii) the object comprising a red color and(iii) the spatial location of the object in the field of view of saidimager, and (b) image processing of captured image data by said imageprocessor comprises determination that an object present forward of theequipped vehicle is a caution sign based upon at least one of (i) theobject comprising a triangular shape, (ii) the object comprising ayellow color and (iii) the spatial location of the object in the fieldof view of said imager.
 80. The image sensing system of claim 69,wherein said imager is accommodated in a body that is attached at anin-cabin surface of a windshield of a vehicle.
 81. An image sensingsystem for a vehicle, said image sensing system comprising: an imagercomprising a two-dimensional CMOS photosensor array of light sensingphotosensor elements; wherein said imager is disposed at or proximate toan in-cabin portion of a windshield of a vehicle equipped with saidimage sensing system, and wherein said imager has a forward field ofview to the exterior of the equipped vehicle through the windshield ofthe equipped vehicle; wherein said photosensor array is operable tocapture image data; a control comprising an image processor; whereinsaid image sensing system identifies objects in said forward field ofview of said imager via processing of captured image data by said imageprocessor; wherein said photosensor array is operable to capture framesof image data; wherein said photosensor array of light sensingphotosensor elements comprises at least 262,144 photosensor elements;and wherein said imager comprises a lens.
 82. The image sensing systemof claim 81, wherein said imager has a forward field of view to theexterior of the equipped vehicle through the windshield of the equippedvehicle at a region of the windshield that is swept by a windshieldwiper of the equipped vehicle.
 83. The image sensing system of claim 81,wherein, at least in part responsive to image processing of capturedimage data by said image processor, said image sensing system isoperable to identify at least one of (i) approaching headlights, (ii)leading taillights, (iii) lane markers, (iv) traffic signs, (v) trafficlights, (vi) stop signs and (vii) caution signs.
 84. The image sensingsystem of claim 81, wherein said image sensing system includes anexposure control which determines an accumulation period of time thatsaid photosensor array senses light when capturing a frame of imagedata.
 85. The image sensing system of claim 81, comprising a spectralfilter, wherein light emitted by sources external of the equippedvehicle and/or reflected by objects external of the equipped vehiclepasses through, and is filtered by, said spectral filter to be incidenton at least some of said light sensing photosensor elements of saidphotosensor array.
 86. The image sensing system of claim 85, whereinsaid spectral filter substantially attenuates light having a wavelengthgreater than about 830 nanometers.
 87. The image sensing system of claim85, wherein said spectral filter comprises a red filter that passesvisible light of wavelength generally in the red portion of the visiblespectrum and that substantially attenuates light having wavelengthsgenerally outside the red portion of the visible spectrum.
 88. The imagesensing system of claim 85, wherein said spectral filter comprises a redcomplement filter that substantially passes wavelengths generallyoutside the red portion of the visible spectrum and that substantiallyattenuates wavelengths generally in the red portion of the visiblespectrum.
 89. The image sensing system of claim 85, wherein saidphotosensor array of light sensing photosensor elements, said lens andsaid spectral filter are housed within an imager module.
 90. The imagesensing system of claim 85, wherein said spectral filter is disposedbetween said lens and said photosensor array of light sensingphotosensor elements.
 91. An image sensing system for a vehicle, saidimage sensing system comprising: an imager comprising a two-dimensionalCMOS photosensor array of light sensing photosensor elements; whereinsaid imager is disposed at or proximate to an in-cabin portion of awindshield of a vehicle equipped with said image sensing system, andwherein said imager has a forward field of view to the exterior of theequipped vehicle through the windshield of the equipped vehicle; whereinsaid imager has a forward field of view to the exterior of the equippedvehicle through the windshield of the equipped vehicle at a region ofthe windshield that is swept by a windshield wiper of the equippedvehicle; wherein said photosensor array is operable to capture imagedata; a control comprising an image processor; wherein said imagesensing system identifies objects in said forward field of view of saidimager via processing of captured image data by said image processor;wherein said photosensor array is operable to capture frames of imagedata; wherein said photosensor array of light sensing photosensorelements comprises at least 262,144 photosensor elements; wherein saidimager comprises a lens and a spectral filter; and wherein light emittedby sources external of the equipped vehicle and/or reflected by objectsexternal of the equipped vehicle passes through, and is filtered by,said spectral filter to be incident on at least some of said lightsensing photosensor elements of said photosensor array.
 92. The imagesensing system of claim 91, wherein, at least in part responsive toimage processing of captured image data by said image processor, saidimage sensing system is operable to identify at least one of (i)approaching headlights, (ii) leading taillights, (iii) lane markers,(iv) traffic signs, (v) traffic lights, (vi) stop signs and (vii)caution signs.
 93. The image sensing system of claim 91, wherein saidimage sensing system includes an exposure control which determines anaccumulation period of time that said photosensor array senses lightwhen capturing a frame of image data.
 94. The image sensing system ofclaim 91, wherein said spectral filter substantially attenuates lighthaving a wavelength greater than about 830 nanometers.
 95. The imagesensing system of claim 91, wherein said spectral filter comprises a redfilter that passes visible light of wavelength generally in the redportion of the visible spectrum and that substantially attenuates lighthaving wavelengths generally outside the red portion of the visiblespectrum.
 96. The image sensing system of claim 91, wherein saidspectral filter comprises a red complement filter that substantiallypasses wavelengths generally outside the red portion of the visiblespectrum and that substantially attenuates wavelengths generally in thered portion of the visible spectrum.
 97. The image sensing system ofclaim 91, wherein said photosensor array of light sensing photosensorelements, said lens and said spectral filter are housed within an imagermodule.
 98. The image sensing system of claim 97, wherein said spectralfilter is disposed between said lens and said photosensor array of lightsensing photosensor elements.